Reassessing the Past Century of Warming in Australia

Reference
Stockwell, D.R.B. and Stewart, K. 2012. Biases in the Australian high quality temperature network. Energy and Environment23: 1273-1294.

Introducing their study, Stockwell and Stewart (2012) write that "various reports identify global warming over the last century as around 0.7°C, but warming in Australia at around 0.9°C, suggesting Australia may be warming faster than the rest of the world." But is that really the case?

In an effort designed to answer this question, Stockwell and Stewart evaluated "potential biases in the High Quality Network (HQN) compiled from 100 rural surface temperature series from 1910 due to: (1) homogeneity adjustments used to correct for changes in location and instrumentation, and (2) the discrimination of urban and rural sites." More specifically, their approach was "to compare the HQN with a new network compiled from raw data using the minimal adjustments necessary to produce contiguous series, called the Minimal Adjustment Network (MAN)."

According to the two researchers, results comparison found that "the average temperature trend of the MAN stations was 31% lower than the HQN," and they state that "by a number of measures, the trend of the Australian MAN is consistent with the global trend." Additional problems that they encountered with the HQN database included "failure of homogenization procedures to properly identify errors, individual sites adjusted more than the magnitude of putative warming last century, and some sites of such poor quality they should not be used, especially under a 'High Quality' banner."

Simply put, Stockwell and Stewart conclude that biases from the above-mentioned problems "have exaggerated apparent Australian warming." And when those exaggerations are properly addressed, their analysis suggests that Australia appears to have warmed to about the same degree as the rest of the world over the past century.